We are producing a collection of continuous hybrid cell lines secreting monospecific antibodies of selected and defined specificities -antibodies against a series of well defined haptens and against human cell surface antigens. These hybridomas are made between mouse myelomas and mouse spleen cells. The antibodies will be used to study the genetics of mouse B cell differentiation and immunoglobulin production. The mouse B cell repertoire and its development from "germ line" genetic information will be analyzed. Antibodies against human tumor antigens and differentiation antigens will be used to detect and purify these antigens and to analyze their expression on mouse-human hybrids. Those against antigens such as HLA will be made available for human lymphocyte typing.